Punches

ABSTRACT

The tool steel bar which is to form the punch is placed within the oversized cavity of the hollow die and is thereafter deformed under the action of the shaped die slide member. The cavity is provided with a plug having a formed upper surface so as to impart a predetermined configuration to the head of the punch, for example, for impressing a signature or other identification into subsequently formed tablets.

United States Patent Juffs [451 Mar. 21, 1972 [54] PUNCHES [56] References Cited [72] Inventor: Christopher Paul J ufls, Toton, England UNITED STATES PATENTS [73] Assignee: I Holland Limited, Long Eaton, Not- 3,209,453 10/1965 Bertoglio et al... 72/35 8 X tingham, England 3,406,555 10/1968 Fuchs ..72/377 g 2,755,689 7 1 56 db k 22 Filed: June 8, 1970 I 9 ac X [21 1 App]. 44,028 Primary Examiner-Bamard Stickney Attorney-Kenyon & Kenyon Reilly Carr & Chapin [30] Foreign Application Priority Data [57] ABSTRACT June 7, 1969 'Great Britain ..28,9l8/69 The tool steel bar which is to form the punch is placed within the oversized cavity of the hollow die and is thereafter [52] US. Cl. ..76/107 R, 72/358, 72/377 deformed under the action of the shaped die slide member. [51] Int. Cl ..B21k 5/20 The cavity is provided with a plug having a formed upper sur- [58] Field of Search ..76/107 R; 72/377, 358 face so as to impart a predetermined figu to t ad of the punch, for example, for impressing a signature or other identification into subsequently formed tablets.

9 Claims, 1 Drawing Figure PATENTEDMARZI 1912 nv VENTOR CHRIS'TODHEF? PAL/L Jul- 5 PUNCHES This invention is for improvements in or relating to punches and has for one object to provide an improved method for the manufacture of punches with a Head of larger diameter than the body, particularly punches of the kind used in the manufacture of tablets as for example pharmaceutical tablets, and in so doing improving the strength and resistance to abrasive wear to which the Head of this type of punch is subjected in use. I

It will be appreciated that tablets are made by depositing a predetermined quantity of powder into a die and compressing the powder. The compressing is usually done by lowering and raising punches under pressure on to the powdered material in the die. Such punches are usually provided with a recessed end portion so that the tablet shall have a domed or bevelled part and the recessed portion of the punch may have some other marking such as an initial letter or name or the like either standing proud or recessed in order to give identification to the tablet.

The formation of the kind of punch with which the present invention is concerned has previously been by conventional methods as for example by taking a bar of appropriate tool steel, impressing the recessed portion and turning and grinding the bar down to appropriate diameter. This process is time consuming and expensive since tool steel is comparatively expensive and since a comparatively large quantity (55 percent) of the tool steel in original bar form is turned and ground to useless swarf.

The present invention seeks to provide a method for the forming of punches without the need to turn and grind substantial quantities of steel.

Accordingly the present invention provides a method of forming a punch especially a punch for use with a Rotary Tablet forming machine comprising, locating a bar of tool steel in a hollow die, said bar being of lesser diameter and longer in length than the final punch, closing the end of said die with a member adapted to slide within said die, applying a force to said member to flow the steel of said bar into the form of said die.

According to the present invention a bar of steel of substantially the same volume as the finished punch is first obtained, said bar being of lesser diameter and longer in length than the final punch dimensions. Such a bar is located in a die, one end of which will be provided with the shape for the end of the punch and will include any marking such as for example letters or names in either relief or recessed form; the die at the other end having a member slidable therein also of appropriately shaped form so that when the bar has been located in the die the member is either pressed by a hydraulic or other press or is hit by a hammer in such a way as to flow the steel of the bar in plastic form into the shape of the die. It is found that four to two blows of 100 ton hammer or 200 tons of hydraulic pressure may be appropriate for flowing cold alloy tool steel of the following compositions Alley I Alloy 2 C 1.00 0.53

Mn 0.85 Cp 0.75 1.80 W 0.40 1.90

into a punch approximately 13 cm. long and 2 cm. in diameter or 13 cm. long and 3 cm. in diameter.

in order that the present invention may be more readily understood reference is now made to the drawing which illustrates in cross section a die according to the present invention.

In the FIGURE a die body 1 has a hollow die chamber 3. A removable plug 2 closes one end of the chamber 3. The plug 2 can be provided with a hemispherical portion 9 which itself may have a recessed letter nor a name formed therein. A bar of die or punch steel 4 is located within the chamber 3. The upper end of the chamber 3 is closed by a ring 5 accurately located in alignment with the die body 1 b a chamfered peripheral ring 6. A shaped member 7 is slldab e within a bore formed in the ring 5 and closes the end of the die chamber by applying force to the member 7 until such time as its upper surface is flush with the upper surface of the ring 5. The tool steel bar 4 is forced to flow into the form of the hollow die 3 and to flow into the shape formed by a hemispherical portion 9 and by the recessed portion 8 of the member 7. The punch may be extracted from the die by pulling portion 5 away from the die body 1. Such a punch may be formed with the tool steel cold, or it may be raised to an elevated temperature beneath the dull glowing temperature of the steel.

What we claim is:

l. A method of cold forming a finished punch comprising the steps of locating a bar of high carbon tool steel in a hollow die, said bar being of a lesser diameter than said die;

slidably positioning a member in one end of said die to close said end of said die;

applying a force to said member to move said member against said bar to cause said bar to flow into a punch having the form of said die; and

extracting the finished punch from said die.

2. A method according to claim 1 in which the tool end of said die is provided with a shaped form corresponding to the tablet to be formed by said punch when formed.

3. A method according to claim 1 in which the member slidable relative to said die is struck by a hammer.

4. A member according to claim 1 wherein said member slidable relative to said die is acted on by a hydraulic press.

5. In a method of cold forming a finished punch for a rotary tablet forming machine comprising the steps of providing a die body having a hollow die chamber of predetermined diameter;

positioning a removable plug in a lower end of said body to close said chamber;

positioning a ring on the upper end of said body in alignment with said chamber;

locating a bar of high carbon tool steel in said chamber, said bar being of a lesser diameter than said chamber and of a longer length than said chamber;

slidably mounting a shaped member in said ring to close the upper end of said chamber; applying 'a force to said member to move said member against said bar to cause said bar to flow into a finished punch having a diameter equal to said diameter of said chamber and a length less than said length of said bar; and

pulling said ring from said body to extract said finished punch from said die chamber.

6. A method as set forth in claim 1 wherein said plug has a surface facing said bar of a predetermined shape corresponding to a tablet to be formed by said punch.

7. A method as set forth in claim 1 wherein said bar is made of an alloy of a composition consisting of 1.00 c, 0.85 Mn, 0.75 Cp and 0.40 W.

8. A method as set forth in claim 1 wherein said bar is made of an alloy of a composition consisting of 0.53 C, 1.80 Cp, 1.90 W and 0.20 V.

9. A punch made in accordance with the method of claim 1. 

1. A method of cold forming a finished punch comprising the steps of locating a bar of high carbon tool steel in a hollow die, said bar being of a lesser diameter than said die; slidably positioning a member in one end of said die to close said end of said die; applying a force to said member to move said member against said bar to cause said bar to flow into a punch having the form of said die; and extracting the finished punch from said die.
 2. A method according to claim 1 in which the tool end of said die is provided with a shaped form corresponding to the tablet to be formed by said punch when formed.
 3. A method according to claim 1 in which the member slidable relative to said die is struck by a hammer.
 4. A member according to claim 1 wherein said member slidable relative to said die is acted on by a hydraulic press.
 5. In a method of cold forming a finished punch for a rotary tablet forming machine comprising the steps of providing a die body having a hollow die chamber of predetermined diameter; positioning a removable plug in a lower end of said body to close said chamber; positioning a ring on the upper end of said body in alignment with said chamber; locating a bar of high carbon tool steel in said chamber, said bar being of a lesser diameter than said chamber and of a longer length than said chamber; slidably mounting a shaped member in said ring to close the upper end of said chamber; applying a force to said member to move said member against said bar to cause said bar to flow into a finished punch having a diameter equal to said diameter of said chamber and a length less than said length of said bar; and pulling said ring from said body to extract said finished punch from said die chamber.
 6. A method as set forth in claim 1 wherein said plug has a surface facing said bar of a predetermined shape corresponding to a tablet to be formed by said punch.
 7. A method as set forth in claim 1 wherein said bar is made of an alloy of a composition consisting of 1.00 c, 0.85 Mn, 0.75 Cp and 0.40 W.
 8. A method as set forth in claim 1 wherein said bar is made of an alloy of a composition consisting of 0.53 C, 1.80 Cp, 1.90 W and 0.20 V.
 9. A punch made in accordance with the method of claim
 1. 